Preface

ArcGIS is an industry-standard geographic information system from ESRI.

This book will show you how to use the Python programming language to create geoprocessing scripts, tools, and shortcuts for the ArcGIS Desktop environment.

This book will make you a more effective and efficient GIS professional, by showing you how to use the Python programming language with ArcGIS Desktop to automate geoprocessing tasks, manage map documents and layers, find and fix broken data links, edit data in feature classes and tables, and much more.

Programming ArcGIS 10.1 with Python Cookbook starts by covering fundamental Python programming concepts in an ArcGIS Desktop context. Using a how-to instruction style, you'll then learn how to use Python to automate common important ArcGIS geoprocessing tasks.

In this book, you will also cover specific ArcGIS scripting topics that will help save you time and effort when working with ArcGIS. Topics include managing map document files, automating map production and printing, finding and fixing broken data sources, creating custom geoprocessing tools, and working with feature classes and tables, among others.

In Programming ArcGIS 10.1 with Python Cookbook, you'll learn how to write geoprocessing scripts using a pragmatic approach designed around accomplishing specific tasks in a cookbook style format.

What this book covers

Chapter 1, Fundamentals of the Python Language for ArcGIS, will cover many of the basic language constructs found in Python. Initially, you'll learn how to create new Python scripts or edit existing scripts. From there, you'll get into language features, such as adding comments to your code, variables, and the built-in typing systems that makes coding with Python easy and compact. Furthermore, we'll look at the various built-in data-types that Python offers, such as strings, numbers, lists, and dictionaries. In addition to this, we'll cover statements, including decision support and looping structures for making decisions in your code and/or looping through a code block multiple times.

Chapter 2, Writing Basic Geoprocessing Scripts with ArcPy, will teach the basic concepts of the ArcPy Python site package for ArcGIS, including an overview of the basic modules, functions, and classes. The reader will be able write a geoprocessing script using ArcPy with Python.

Chapter 3, Managing Map Documents and Layers, will use the Arcpy Mapping module to manage map document and layer files. You will learn how to add and remove geographic layers from map document files, insert layers into data frames, and move layers around within the map document. The reader will also learn how to update layer properties and symbology.

Chapter 4, Finding and Fixing Broken Data Links, will teach how to generate a list of broken data sources in a map document file and apply various Arcpy Mapping functions to fix these data sources. The reader will learn how to automate the process of fixing data sources across many map documents.

Chapter 5, Automating Map Production and Printing, will teach how to automate the process of creating production-quality maps. These maps can then be printed, exported to image file formats, or exported to PDF files for inclusion in map books.

Chapter 6, Executing Geoprocessing Tools from Scripts, will teach how to write scripts that access and run geoprocessing tools provided by ArcGIS.

Chapter 7, Creating Custom Geoprocessing Tools, will teach how to create custom geoprocessing tools that can be added to ArcGIS and shared with other users. Custom geoprocessing tools are attached to a Python script that process or analyze geographic data in some way.

Chapter 8, Querying and Selecting Data, will teach how to execute the Select by Attribute and Select by Location geoprocessing tools from a script to select features and records. The reader will learn how to construct queries that supply an optional where clause for the Select by Attribute tool. The use of feature layers and table views as temporary datasets will also be covered.

Chapter 9, Using the ArcPy Data Access Module to Select, Insert, and Update Geographic Data and Tables, will teach how to create geoprocessing scripts that select, insert, or update data from geographic data layers and tables. With the new ArcGIS 10.1 Data Access module, geoprocessing scripts can create in-memory tables of data, called cursors, from feature classes and tables. The reader will learn how to create various types of cursors including search, insert, and update

Chapter 10, Listing and Describing GIS Data, will teach how to obtain descriptive information about geographic datasets through the use of the Arcpy Describe function. As the first step in a multi-step process, geoprocessing scripts frequently require that a list of geographic data be generated followed by various geoprocessing operations that can be run against these datasets.

Chapter 11, Customizing the ArcGIS Interface with Add-Ins, will teach how to customize the ArcGIS interface through the creation of Python add-ins. Add-ins provide a way of adding user interface items to ArcGIS Desktop through a modular code base designed to perform specific actions. Interface components can include buttons, tools, toolbars, menus, combo boxes, tool palettes, and application extensions. Add-ins are created using Python scripts and an XML file that define how the user interface should appear.

Chapter 12, Error Handling and Troubleshooting, will teach how to gracefully handle errors and exceptions as they occur while a geoprocessing script is executing. Arcpy and Python errors can be trapped with the Python try/except structure and handled accordingly.

Appendix A, Automating Python Scripts, will teach how to schedule geoprocessing scripts to run at a prescribed time. Many geoprocessing scripts take a long time to fully execute and need to be scheduled to run during non-working hours on a regular basis. The reader will learn how to create batch file containing geoprocessing scripts and execute these at a prescribed time.

Appendix B, Five Things Every GIS Programmer Should Know How to Do with Python, will teach how to write scripts that perform various general purpose tasks with Python. Tasks, such as reading and writing delimited text files, sending e-mails, interacting with FTP servers, creating ZIP files, and reading and writing JSON and XML files are common. Every GIS programmer should know how to write Python scripts that incorporate this functionality.

What you need for this book

To complete the exercises in this book, you will need to have installed ArcGIS Desktop 10.1 at either the Basic, Standard, or Advanced license level. Installing ArcGIS Desktop 10.1 will also install Python 2.7 along with the IDLE Python code editor

Who this book is for

Programming ArcGIS 10.1 with Python Cookbook is written for GIS professionals who wish to revolutionize their ArcGIS workflow with Python. Whether you are new to ArcGIS or a seasoned professional, you almost certainly spend time each day performing various geoprocessing tasks. This book will teach you how to use the Python programming language to automate these geoprocessing tasks and make you a more efficient and effective GIS professional.

Conventions

In this book, you will find a number of styles of text that distinguish between different kinds of information. Here are some examples of these styles, and an explanation of their meaning.

Code words in text are shown as follows: " we have loaded the ListFeatureClasses.py script with IDLE."

A block of code is set as follows:

import arcpy
fc = "c:/ArcpyBook/data/TravisCounty/TravisCounty.shp"
# Fetch each feature from the cursor and examine the extent properties and spatial reference
for row in arcpy.da.SearchCursor(fc, ["SHAPE@"]):
  # get the extent of the county boundary
  ext = row[0].extent
  # print out the bounding coordinates and spatial reference
  print "XMin: " + ext.XMin
  print "XMax: " + ext.XMax
  print "YMin: " + ext.YMin
  print "YMax: " + ext.YMax
  print "Spatial Reference: " + ext.spatialReference.name

When we wish to draw your attention to a particular part of a code block, the relevant lines or items are set in bold:

import arcpy

fc = "c:/data/city.gdb/streets"

# For each row print the Object ID field, and use the SHAPE@AREA
# token to access geometry properties

with arcpy.da.SearchCursor(fc, ("OID@", "SHAPE@AREA")) as cursor:
  for row in cursor:
    print("Feature {0} has an area of {1}".format(row[0], row[1]))

Any command-line input or output is written as follows:

[<map layer u'City of Austin Bldg Permits'>, <map layer u'Hospitals'>, <map layer u'Schools'>, <map layer u'Streams'>, <map layer u'Streets'>, <map layer u'Streams_Buff'>, <map layer u'Floodplains'>, <map layer u'2000 Census Tracts'>, <map layer u'City Limits'>, <map layer u'Travis County'>]

New terms and important words are shown in bold. Words that you see on the screen, in menus or dialog boxes for example, appear in the text like this: "go to Start | Programs | ArcGIS | Python 2.7 | IDLE".

Note

Warnings or important notes appear in a box like this.

Tip

Tips and tricks appear like this.

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